Abstract
Objective To investigate the role of cervical sympathetic nerve in the development of chronic compression of the brachial plexus.Methods Twenty-four male Sprague-Dawley rats were randomly divided into 3 groups with 8 mrs per group.Lower trunk chronic compression was created in rats of group A and group B.In addition,the middle cervical sympathetic ganglions were resected in rats of group B.Group C served as normal control.Three months after the compression surgery,compound muscle action potentials (CMAPs) of the first interosseus were obtained to record CMAP latency and amplitude.A 3 mm long nerve segment of the distal part of the compressed lower tnmk was harvested and semi-thin sections were collected for toluidine blue staining.The number of myehnated nerve fibers was counted.The C8 and T1 dorsal mot ganglia (DRG) were harvested to detect the mRNA expression level of substance P (SP) using RT-PCR.Results CMAP amplitude was (2.2 ± 1.1) mV,(3.9 ± 1.1) mV and (8.6 ± 2.0) mV in group A,B and C,respectively.The differences of the amplitudes among group A,B and C (group A ＜ group B ＜ group C) were significant (P ＜ 0.01).CMAP latency was(4.8 ± 0.9)ms,(3.9 ± 0.5)ms and (2.8 ± 0.2)ms in group A,B and C,respectively,the differences (group A ＞ group B ＞ group C) also being statistically significant (P ＜ 0.01).The total number of myelinated nerve fibers (group A ＜ group B ＜ group C) was (3583 ± 540),(5098 ± 742),(7934 ± 868),respectively.The difference was significant (P＜0.01).The level of SP mRNA (group A＞ group B＞ group C) was (3.6±0.8) × 10-2,(2.2 ± 0.7) × 10-2,(1.2±0.3) × 10-2,respectively,being significantly different among the groups (P ＜ 0.01).Condusion The existence of cervical sympathetic nerve can worsen the degree of brachial plexus lesion due to chronic compression.It causes increase in the expression of substance P in dorsal root gangha.Sympathetic gangha resection helps to lower the lesion degree and relieve the pain induced by chronic compression.Sympathetic irritation may be a co-factor in the development of peripheral nerve chronical compressive diseases. Key words: Ganglia, sympathetic; Brachial plexus; Models, animal; Nerve entrapments
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